From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-Id: <20111207165602.489306609@clark.kroah.org> Date: Wed, 07 Dec 2011 08:54:58 -0800 From: Greg KH To: , Cc: , , , Ido Yariv , Thomas Gleixner Subject: [25/27] genirq: Fix race condition when stopping the irq thread In-Reply-To: <20111207165611.GA19872@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: 2.6.32-longterm review patch. If anyone has any objections, please let me know. ------------------ From: Ido Yariv commit 550acb19269d65f32e9ac4ddb26c2b2070e37f1c upstream. In irq_wait_for_interrupt(), the should_stop member is verified before setting the task's state to TASK_INTERRUPTIBLE and calling schedule(). In case kthread_stop sets should_stop and wakes up the process after should_stop is checked by the irq thread but before the task's state is changed, the irq thread might never exit: kthread_stop irq_wait_for_interrupt ------------ ---------------------- ... ... while (!kthread_should_stop()) { kthread->should_stop = 1; wake_up_process(k); wait_for_completion(&kthread->exited); ... set_current_state(TASK_INTERRUPTIBLE); ... schedule(); } Fix this by checking if the thread should stop after modifying the task's state. [ tglx: Simplified it a bit ] Signed-off-by: Ido Yariv Link: http://lkml.kernel.org/r/1322740508-22640-1-git-send-email-ido@wizery.com Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman --- kernel/irq/manage.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/kernel/irq/manage.c +++ b/kernel/irq/manage.c @@ -475,8 +475,9 @@ static irqreturn_t irq_nested_primary_ha static int irq_wait_for_interrupt(struct irqaction *action) { + set_current_state(TASK_INTERRUPTIBLE); + while (!kthread_should_stop()) { - set_current_state(TASK_INTERRUPTIBLE); if (test_and_clear_bit(IRQTF_RUNTHREAD, &action->thread_flags)) { @@ -484,7 +485,9 @@ static int irq_wait_for_interrupt(struct return 0; } schedule(); + set_current_state(TASK_INTERRUPTIBLE); } + __set_current_state(TASK_RUNNING); return -1; }